Abstract: Cloud storage has become a trend and more practical in recent years. This unique feature of the cloud poses many security challenging design issues. One of the most important security aspects that need to be addressed is that to assure the integrity of clients data stored in the cloud. In this paper, we propose a RSA-based dynamic public audit service for the integrity verification of data using Sobol sequence. Our scheme allows a third party auditor (TPA) on behalf of the clients to verify the integrity of data stored in the cloud and also supports data dynamics at block level while maintaining the same integrity assurance. Our model allows probabilistic proofs of integrity by challenging random blocks from the server which drastically reduces the computation and communication overhead. The security, performance analysis and experimental results show that our scheme is more secure and efficient than existed probability verification schemes.